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exam 2
semester 2
19
Organic Chemistry
Undergraduate 2
03/12/2013

Additional Organic Chemistry Flashcards

 


 

Cards

Term
benzaldehyde
Definition
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Term
Tollen's Reagent
Definition
Ag2O - reacts ONLY with aldehydes, turning them into carboxylic acids
Term
aldehydes are more reactive than ketones; why?
Definition

- steric reasons - aldehydes are more open to nucleophilic attack (less substituent groups)

 

- electronic reasons - there are two R-groups on ketones, which are electron donating groups that stabilize the positive charge on C and makes it less polarized and therefore less reactive

Term
if you add H2O to a ketone and to an aldehyde, creating in both cases a geminal diol, where will the equilibrium lie?
Definition

ketone: equilibrium will lie toward the ketone because it is less reactive due to steric and electronic reasons.

 

aldehyde: equilibrium will lie towards the geminal diol because an aldehyde is very reactive to nucleophilic substitution because of a lack of steric strain and fewer EDG to stabilize the partial positive charge on carbon

Term
why does imine and enamine formation work best in acidic (but not TOO acidic) environments?
Definition
need acid to donate a proton to make OH into OH2 to make it a good leaving group; but you also need a little base later on to abstract a proton.
Term
Wolff-Kishner Reaction
Definition
making a ketone or an aldehyde into a carbonyl using H2NNH2; has a hydrazone intermediate
Term
define: ketal/acetal
Definition
ketal is the general name for a carbon with two -OR groups attached; it's achieved by reacting a ketone with 2ROH and an acid catalyst, is reversible using large amounts of excess acid. "acetal" is the specific name used for when you started with an aldehyde.
Term
would an imine/enamine be expected to undergo 1,2 or 1,4 addition preferentially? Why?
Definition
1,4 addition preferentially - because they are reversible reactions, they are at equilibrium and assume the more stable final product.
Term
why will a 1,4 conjugate addition of (R)2CuLi not work on an aldehyde?
Definition
if it's not sterically hindered enough, you'll also get 1,2 addition
Term
which is more stable, RSH or RSSR?
Definition
RSSR
Term
Williamson Ether Synthesis
Definition
using NaH
Term
basically the only thing that doesn't react in alkoxymercuration of alkenes is a ditertiary ether. Why not?
Definition
It's too sterically hindered.
Term
how is base-catalyzed ring opening different from acid-catalyzed?
Definition

acid-catalyzed: if there's an option to form a tertiary carbocation, it will be formed. Otherwise, the less sterically-hindered site will form.

 

base-catalyzed: there is no carbocation intermediate, so you only consider steric strain when you look to see where attack will be.

Term
why are dimethyl sulfides more reactive than ethers?
Definition
sulfur is bigger and hence more reactive, so a good nucleophile
Term
why does water force a micelle structure?
Definition
to minimize the contact it has with the micelle, which forces it to be ordered (decrease entropy).
Term
why are carboxylic acids more acidic than alcohols?
Definition
because resonance stablizes their ion
Term
define: buffer
Definition
a mix of an acid and its conjugate base that resists change in pH
Term
what is the Henderson-Hasselback equation?
Definition
pH = pKa + log (base/acid)
Term
what are the two things that determine the reactivity of carboxylic acids/derivatives?
Definition

1. steric factors - less substitution means more reactive.

 

2. -NH2 < -OR < -O-C=OR < X

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